Would you recommend every 3K miles? What oil should I use? In the manual it does not say. I believe the past owner used Castrol for their last oil...\


Please help, wondering what oil I should use and what grade.

 

Regarding Brand of oil, it doesn't matter much. BUT use the same type (As in mineral or synthetic) oil. As for the grade of the oil, go check your maintenance booklet.

 

I use 10/40 semi synthetic diesel formulated oil in my 300D......this is as per the manual. I change every 3000 miles

You can run 0/40 synthetic as well....I am looking to do this next time, as I have some lifter tick at start up. On synthetic I will run for 5000 miles before changing it.

 

so it does not have to be the same oil when you change it.

 

Kind of......10/40 semi synthectic and 0/40 synthetic are in the same kind of range in terms of the upper temperature range, however, the 0/40 synthetic will give better protection in cold temperatures as the oil will be thinner.

Make sure you change your oil filter.

 

Mobil Delvac 1 works well, changed every 7500 miles has been fine for both my cars, 1984 330,000+ miles and 1993 198,000+ miles

 

Does not matter what type of oil you choose to use, really, so long as the oil viscocity index is approved in the owners manual for the ambient temperature you typically run the car in. Currently, I am running Mobile 1 15W-50 in my 300E, but I'll change that out to Rotella 5W-40 when it gets a bit colder.

Brand names don't matter so much, although some are better than others. What really matters is changing the oil more often, which kind of nullifies the purchase of more expensive oil. "Change it hot, and change it often" is a very good motto.

As for don't mix synthetic and mineral oil....bah! All oil manufacturers out there now have synthetic mineral blended oils. In the olden days of yore, before all oils had detergent additives in them, you didn't want to switch brands of oil because you never knew if you were going to run across a cheap oil freak, who always ran on non-detergent oil. On a motor like that, if you then put in a quality detergent oil it would loosen up all the sludge and gum up the motor and filter. Hasn't been a worry that I know of since the 70's. By definition, if there is a S.A.E. rating on the oil (Society of Automotive Engineers), then it is compatible with all other oils. You mentioned Castrol oil. I personally like that oil. Not too expensive and very good quality, although I don't like their synthetic oil.

Then only thing I am not cheap on is oil filters. With those I stick mostly to MB OEM filters, or NAPA Gold filters. I have heard that VW filters are the same as MB OEM, and a bit cheaper, so I might check those out sometime. I absolutely DON'T use Fram filters. However, on your 300D isn't there an internal type filter element? As opposed to the spin on cartridge filter on my 300E. It might make the lower Fram filter quality less of an issue since they don't have to manufacture the canister. Don't forget to change out the filter.